1. Field of the Disclosure
The present disclosure relates to a keyless entry device for a vehicle, which performs control of causing the equipment of the vehicle to operate, under the condition that authentication based on wireless communication that has been established between an on-vehicle device and a portable device a user possesses.
2. Description of the Related Art
An example of on on-vehicle device remote controller known as a smart key system has been disclosed in Japanese Unexamined Patent Application Publication No. 2009-68255. This on-vehicle device remote controller regularly transmits an activation signal by wireless (a regular transmission method) from an antenna on a vehicle side to a vehicle exterior area, and when mutual authentication has been established upon receiving a response from the portable device of a user, which has received that activation signal, the on-vehicle device remote controller controls an operation of unlocking a door in a locked state.
In particular, the above-mentioned related art focuses its attention on a point that when, in a situation where many vehicles equipped with remote controllers of the same type are parked, activation signals are transmitted with same timing from a plurality of vehicles adjacent to one another, signals are degraded owing to communication interference. Namely, in the relate art, an activation signal to be transmitted from an on-vehicle device is preliminarily set as a PN code (pseudo-noise sequence code), and a portable device corresponding to this is also caused to hold a PN code. Accordingly, even if communication interference has occurred, by calculating a correlation value between the PN code received by the portable device and the self-PN code, it is possible to realize the authentication of a legitimate user with a high probability.
Usually, an ID code unique to a vehicle is used for authentication between an on-vehicle device and a portable device, performed in a keyless entry device. The ID code unique to a vehicle is held in each of the on-vehicle device and the portable device, and hence it is possible for the on-vehicle device and the portable device to correctly recognize a correspondence relationship therebetween (mutual authentication).
In addition, it is necessary for the ID code to be unique to each of many vehicles, and so as to avoid overlap between a plurality of vehicles, the ID code is described with a certain amount of bit length (for example, 24 bits). In this regard, however, in the sequence of the mutual authentication, it is not necessary to use all 24 bits in a stage where an activation signal or the like is initially transmitted form an on-vehicle device to a portable device, and it is only necessary to use a portion of 24 bits. For example, if, from among all 24 bits of the ID code, the lower 8 bits thereof is only used for an ID abbreviated for activation, it is possible to reduce a communication time by a corresponding amount, and it may be considered that it is possible to improve the responsiveness of a system.
However, while a method in which an ID code is abbreviated and used for a trigger for activation or the like is useful in reducing a communication time, the method induces an unexpected failure to occur in some cases, according to circumstances. For example, it is assumed that an activation signal transmitted from an on-vehicle device to a portable device is used for a plurality of different purposes (used for unlocking a door, a welcome operation, and the like). When the portable device of a legitimate user exists in the neighborhood of a vehicle (within a communication area), an activation signal used for unlocking a door, from among these purposes, is a signal used for unlocking a door on the basis of a simple touch operation, for example. In addition, an activation signal used for the welcome operation is a signal used for causing lams and lights to be turned on or blink on and off and promoting the existence of the self-vehicle when the portable device of the legitimate user approaches the vehicle.
If an abbreviated ID is used for each of these plural purposes, while the ID codes do not coincide with one another as a whole, when abbreviated IDs are compared with one another, it is highly likely that overlaps occur between a plurality of vehicles. Therefore, for example, when a same user possesses a plurality of vehicles (for example, vehicles A and B), and approaches one vehicle A with having two portable devices A and B paired with the vehicles A and B, respectively, even if the ID codes of the vehicles A and B do not coincide with each other, an abbreviated ID used for unlocking in one vehicle A coincides with an abbreviated ID used for a welcome operation in the other vehicle B by chance, in some cases.
In this case, if an activation signal used for unlocking is transmitted from the vehicle A, since the portable device B, which has received the activation signal, recognizes that an activation signal used for a welcome operation has been transmitted from the vehicle B, a response signal turns out to be transmitted from the portable device B to the vehicle A that is properly supposed to not to be paired. Therefore, even if the portable device A normally transmits a response signal, a communication failure occurs owing to responses from the two portable devices A and B, and the operation of a system is likely to become unstable.
These and other drawbacks exist.